1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a structure of DRAM (Dynamic Random Access Memory) including a capacitor dielectric film made of a material having a large dielectric constant and a manufacturing method therefor.
2. Related Background Art
Hitherto, DRAM has been widely employed as one of semiconductor devices permitting information to be input and output randomly. In general, DRAM has a memory cell array portion serving as a storage region for storing a multiplicity of information items to be stored and peripheral circuit portions required to input and output information to and from outside.
FIG. 21 is a block diagram showing the structure of a general DRAM.
As shown in FIG. 21, a DRAM 150 has a memory cell array 151 for storing information, a row-and-column address buffer 152 for receiving, from outside, an address signal for selecting a memory cell forming a unit storage circuit, a row decoder 153 and a column decoder 154 which decode the address signal to appoint a memory cell, a sense refresh amplifier 155 for amplifying and reading signals stored in the appointed memory cell, a data-in buffer 156 and a data-out buffer 157 for inputting and outputting data, and a clock generator 158 for generating a clock signal.
The memory cell array 151 having a large area on the semiconductor chip has a plurality of memory cells arranged to store unit storage information and formed into a matrix configuration. In general, one memory cell is composed of one MOS (Metal Oxide semiconductor) transistor and one capacitor connected to the MOS transistor. A memory cell of the foregoing type is called a 1-transistor and 1-capacitor type memory cell. Since a memory cell of this type has a simple structure, the degree of integration of the memory cell array 151 can easily be raised. Therefore, the foregoing memory cells have been employed widely in DRAM having large capacities.
The memory cells of the DRAM can be classified into some types depending upon the structure of the capacitor. Capacitors of a type called a stacked capacitor are included in the capacitors of the memory cells. The stacked capacitor has a structure such that the major portion of the capacitor is extended to the position above the gate electrode and the field oxide film so that the areas of the opposite portions of the electrodes of the capacitors are enlarged.
Since the stacked capacitor has the foregoing characteristic, a required capacity of the capacitor can easily be obtained even if the device is fined due to raising of the degree of integration of the semiconductor device. As a result, stacked capacitors have been employed widely in the trend of the degree of integration of the semiconductor devices being raised. However, if the stacked capacitor is employed in a further fined device, example, a 256 M bit DRAM, a predetermined capacity of the capacitor cannot easily be obtained with the foregoing stacked capacitor.
Accordingly, the capacity of the capacitor has been enlarged by performing an attempt such that a dielectric film, for example, PZT (lead zirconate titanate) having a large dielectric constant, is employed as the dielectric film for the capacitor. FIG. 22 shows an example of a DRAM comprising a dielectric film for a capacitor, the dielectric film being made of a material, such as, PZT, having a large dielectric constant.
As shown in FIG. 22, a P-type semiconductor substrate 101 has a major surface in which a field oxide film 102 is formed in a device separated region of the major surface. A device region on the major surface of the semiconductor substrate 101 has transfer gate transistors 103a and 103b formed thereon.
The transfer gate transistor 103a has a gate electrode 104b formed, through a gate insulating film 105, on a channel region 121 between N-type impurity regions 106c and 106a formed apart from each other on the major surface of the semiconductor substrate 101 to serve as source and drain regions.
The transfer gate transistor 103b has a gate electrode 104c formed, through the gate insulating film 105, on the N-type impurity regions 106a and 106b, serving as the source and drain regions, and the channel region 121 between the impurity regions 106a and 106b. 
On the field oxide film 102, there is extended a gate electrode 104d of another transfer gate transistor. An oxide film 107 is formed to cover the gate electrodes 104b, 104c and 104d. On the impurity region 106a, there is formed a buried bit line 108 so as to be electrically connected to the impurity region 106a. An insulating layer 109 is formed to cover the buried bit line 108.
A first interlayer insulating film 110 is formed to cover the insulating film 109 and the oxide film 107. The top surface of the first interlayer insulating film 110 is flattened. The first interlayer insulating film 110 has a contact hole 110a in a portion above the impurity region 106b. 
A plug 111, electrically connected to the impurity region 106b, is formed in the contact hole 110a. A lower electrode 114 of the capacitor, made of platinum or the like, is formed between the top surface of the plug 111 and that of the first interlayer insulating film 110.
A capacitor dielectric film 115 is formed to cover the lower electrode 114 of the capacitor. The capacitor dielectric film 115 is made of PZT, SrTiO3 or the like. An upper electrode 116 of the capacitor is formed to cover the capacitor dielectric film 115. The upper electrode 116 of the capacitor is, in general, made of platinum.
A second interlayer insulating film 117 is formed to cover the upper electrode 116 of the capacitor. The top surface of the second interlayer insulating film 117 is flattened. A first aluminum line layer 118 is formed above the second interlayer insulating film 117 while being apart from the same. A protective film 119 is formed to cover the first aluminum line layer 118. An aluminum line layer 120 is formed on the protective film 119.
The lower electrode 114 of the capacitor, the capacitor dielectric film 115 and the upper electrode 116 of the capacitor form a capacitor 160.
However, the conventional DRAM suffers from the following problems: the conventional DRAM has included the platinum films to form the lower electrode of the capacitor, electrically connected to the major surface of the semiconductor substrate through the opening in the interlayer insulating film, and the upper electrode of the capacitor formed on the capacitor dielectric film.
1) Although the platinum film has an advantage that it does not easily form a reactive layer in the interface with the dielectric film, the platinum film has a poor reactivity and, therefore, it cannot easily be processed.
2) Known materials except platinum, for example, ruthenium, iridium and the like, for forming the electrode, have a problem of a poor adherence with the silicon oxide film serving as the interlayer insulating film when the foregoing material is formed into a thin film.
3) When the capacitor dielectric film is formed, oxidation of the silicon plug taking place due to oxidation of the foregoing material for forming the electrode cannot be prevented. Thus, the contact resistance will be enlarged excessively and the capacitance is reduced undesirably.
4) Moreover, if the material for forming the electrode, such as ruthenium or iridium, is oxidized, the surface of the material is roughened unintentionally, thus raising a problem in that a leakage current is enlarged excessively. In a case where a metal electrode, made of ruthenium or iridium, is formed and then the metal electrode is subjected to heat treatment at high temperature, the surface of the metal electrode is sometimes roughened though the atmosphere is not the oxidizing atmosphere. Thus, there arises a problem in that the leakage current is enlarged excessively.
The present invention was found to overcome the foregoing problems, and a first object of the present invention is to provide a semiconductor device, which can easily be manufactured.
A second object of the present invention is to provide a semiconductor device which has a cell capacitor having a good adhesion between an electrode and an interlayer insulating film.
A third object of the present invention is to provide a semiconductor having a decreased contact resistance and a large capacitance.
A fourth object of the present invention is to provide a semiconductor having a decreased leakage current.
To achieve the foregoing objects, according to a first aspect of the present invention, there is provided a semiconductor device comprising; a semiconductor substrate having a major surface; an interlayer insulating film formed on the major surface of the semiconductor substrate and having an opening formed to reach the major surface of the semiconductor substrate; a connection member disposed within the opening; a capacitor including a lower electrode of a capacitor electrically connected to the major surface of the semiconductor substrate through the-connection member, a capacitor dielectric film formed on the lower electrode of the capacitor and made of a material having a large dielectric constant and an upper electrode of the capacitor formed on the capacitor dielectric film, wherein the lower electrode of the capacitor is a metal electrode, the metal electrode is mainly composed of ruthenium or iridium, and no oxide layer of materials of the metal electrode is formed on the surface of the metal electrode when the capacitor dielectric film is formed.
According to a second aspect of the present invention, there is provided a semiconductor device comprising: a semiconductor substrate having a major surface; an interlayer insulating film formed on the major surface of the semiconductor substrate and having an opening formed to reach the major surface of the semiconductor substrate; a connection member disposed within the opening; a capacitor including a lower electrode of a capacitor electrically connected to the major surface of the semiconductor substrate through the connection member, a capacitor dielectric film formed on the lower electrode of the capacitor and made of a material having a large dielectric constant and an upper electrode of the capacitor formed on the capacitor dielectric film, wherein the lower electrode of the capacitor consists of a contact layer and a metal electrode, the metal electrode is mainly composed of ruthenium or iridium, the contact layer is made of silicide of elements forming the metal electrode and held between the metal electrode and the connection member, and no oxide layer of materials of the metal electrode is formed on the surface of the metal electrode when the capacitor dielectric film is formed.
According to a third aspect of the present invention, there is provided a semiconductor device according to the first aspect or the second aspect of the present invention, wherein the top end of the connection member is made to be lower than the surface of the interlayer insulating film by 30 nm or more.
According to a fourth aspect of the present invention, there is provided a semiconductor device according to the first aspect or the second aspect of the present invention, wherein an adhesion layer is formed between the interlayer insulating film and the lower electrode of the capacitor.
According to a fifth aspect of the present invention, there is provided a semiconductor device according to the second aspect of the present invention, wherein an adhesion layer is formed between the interlayer insulating film and the lower electrode of the capacitor and the contact layer is composed of at least either of silicide of elements forming the adhesion layer or silicide of elements forming the lower electrode of the capacitor.
According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming an interlayer insulating film on a major surface of a semiconductor substrate, the interlayer insulating film having an opening formed to reach the major surface; burying a connection member in the opening; forming a thin metal film made or mainly composed of ruthenium or iridium as the major component thereof, serving as a lower electrode of the capacitor to be electrically connected to the major surface of the semiconductor substrate through the connection member, and then processing the thin metal film into a predetermined lower electrode structure of the capacitor; and sequentially forming, on the metal electrode, a capacitor dielectric film, made of a material having a large dielectric constant, and an upper electrode of the capacitor in such a manner that no oxide layer of materials of the metal electrode is formed on the surface of the metal electrode.
According to a seventh aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming an interlayer insulating film on a major surface of a semiconductor substrate, the interlayer insulating film having an opening formed to reach the major surface; burying a connection member containing silicon as the major no component thereof in the opening; forming a thin metal film made or mainly composed of ruthenium or iridium, serving as a lower electrode of the capacitor to be electrically connected to the major surface of the semiconductor substrate through the connection member, and then processing the thin metal film into a predetermined lower electrode structure of the capacitor; performing heat treatment in such a manner that a silicide layer of the thin metal film is formed between the metal electrode and the connection member; and sequentially forming, on the metal electrode, a capacitor dielectric film, made of a material having a large dielectric constant, and an upper electrode of the capacitor in such a manner that no oxide layer of materials of the metal electrode is formed on the surface of the metal electrode.
According to an eighth aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming an interlayer insulating film on a major surface of a semiconductor substrate, the interlayer insulating film having an opening formed to reach the major surface; burying a connection member in a portion of the opening; forming a thin metal film made or mainly composed of ruthenium or iridium as the major component thereof, serving as a lower electrode of the capacitor to be electrically connected to the major surface of the semiconductor substrate through the connection member so as to cover the interlayer insulating film and plug the opening, and then processing the thin metal film into a predetermined lower electrode structure of the capacitor; and sequentially forming, on the metal electrode, a capacitor dielectric film, made of a material having a large dielectric constant, and an upper electrode of the capacitor in such a manner that no oxide layer of materials of the metal electrode is formed on the surface of the metal electrode.
According to a ninth aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming an interlayer insulating film on a major surface of a semiconductor substrate, the interlayer insulating film having an opening formed to reach the major surface; burying a connection member containing silicon as the major component thereof in a portion of the opening; forming a thin metal film made or mainly composed of ruthenium or iridium, serving as a lower electrode of the capacitor to be electrically connected to the major surface of the semiconductor substrate through the connection member so as to cover the interlayer insulating film and plug the opening, and then processing the thin metal film into a predetermined lower electrode structure of the capacitor; performing heat treatment in such a manner that a silicide layer of the thin metal film is formed between the metal electrode and the connection member; and sequentially forming, on the metal electrode, a capacitor dielectric film, made of a material having a large dielectric constant, and an upper electrode of the capacitor in such a manner that no oxide layer of materials of the metal electrode is formed on the surface of the metal electrode.
According to a tenth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the sixth to ninth aspects of the present invention and further comprising the step of flattening the surface of the lower electrode of the capacitor by a chemical and mechanical grinding method, the step being performed after the step of forming the lower electrode of the capacitor has been performed.
According to an eleventh aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the sixth to tenth aspects of the present invention and further comprising the step of forming an adhesion layer between the interlayer insulating film and the lower electrode of the capacitor, the step being performed after the step of burying the connection member in the opening of the interlayer insulating film has been performed.
The semiconductor device according to the first aspect of the present invention includes the lower electrode of the capacitor which is the metal electrode, the metal electrode contains ruthenium or iridium as the major component thereof, and the surface of the metal electrode is not oxidized when the capacitor dielectric film is formed. Since the lower electrode of the capacitor is the metal electrode made of iridium or ruthenium, the electrode can easily be processed as compared with the conventional case where platinum is employed to form the electrode. Since the electrode is not oxidized when the capacitor dielectric film is formed, the structure of the cell can be simplified. Since iridium and ruthenium are chemically stable when the capacitor dielectric film is formed, reduction in the capacitance can be prevented. In the case where high temperature heat treatment is performed after the metal electrode has been formed, which is made of iridium or ruthenium, the surface of the metal electrode is sometimes roughened and, thus, the leakage current is sometimes enlarged though the atmosphere is not an oxidizing atmosphere. However, the chemical and mechanical grinding method for flattening the surface will prevent enlargement of the leakage current. When the structure of the capacitor is formed into a stereoscopic cell structure, such as a stacked-type structure and the lower electrode of the capacitor is made of ruthenium or iridium, the capacity of the capacitor can be enlarged.
The semiconductor device according to the second aspect of the present invention enables advantages similar to those obtainable from the semiconductor device according to the first aspect of the present invention to be realized. Since the contact layer made of silicide of elements forming the metal electrode is formed between the metal electrode and the connection member, the contact resistance can be reduced.
The semiconductor device according to the third aspect of the present invention enables advantages similar to those obtainable from the semiconductor device according to the first aspect or the second aspect of the present invention to be realized. Since the top end of the connection member is made to be lower than the surface of the interlayer insulating film, oxidation of the connection member taking place when the capacitor dielectric film is formed can be prevented.
The semiconductor device according to the fourth aspect of the present invention enables advantages similar to those obtainable from the semiconductor device according to the first aspect or the second aspect of the present invention to be realized. Since the adhesion layer is formed between the interlayer insulating film and the lower electrode of the capacitor, the adherence between the interlayer insulating film and the lower electrode of the capacitor can be improved.
The semiconductor device according to the fifth aspect of the present invention enables advantages similar to those obtainable from the semiconductor device according to the second aspect of the present invention to be realized. Since the adhesion layer is formed between the interlayer insulating film and the lower electrode of the capacitor, the adherence between the interlayer insulating film and the lower electrode of the capacitor can be improved. Since the contact layer is made of the silicide of the elements forming the adhesion layer or the silicide of elements forming the lower electrode of the capacitor, the contact resistance can further be reduced.
The method of manufacturing the semiconductor device according to the sixth aspect of the present invention is different from the conventional manufacturing method in that the lower electrode of the capacitor is the metal electrode, the major component element of which is ruthenium or iridium, and the capacitor dielectric film, made of the material having a large dielectric constant, and the upper electrode of the capacitor are formed on the metal electrode in such a manner that no oxide layer of the materials of the metal electrode is formed on the surface of the metal electrode. Therefore, the semiconductor device having the variety of advantages can easily be manufactured.
The method of manufacturing the semiconductor device according to the seventh aspect of the present invention is different from the conventional manufacturing method in that the lower electrode of the capacitor is the metal electrode, the major component element of which is ruthenium or iridium, the silicide layer is formed between the metal electrode and the connection member, and the capacitor dielectric film, made of the material having a large dielectric constant, and the upper electrode of the capacitor are formed on the metal electrode in such a manner that no oxide layer of the materials of the metal electrode is formed on the surface of the metal electrode. Therefore, the semiconductor device having the variety of advantages can easily be manufactured.
The method of manufacturing the semiconductor device according to the eighth aspect of the present invention is different from the conventional manufacturing method in that the lower electrode of the capacitor is the metal electrode, the major component element of which is ruthenium or iridium, and the capacitor dielectric film, made of the material having a large dielectric constant, and the upper electrode of the capacitor are formed on the metal electrode in such a manner that no oxide layer of the materials of the metal electrode is formed on the surface of the metal electrode. Therefore, the semiconductor device having the variety of advantages can easily be manufactured. Since the connection member is buried in only a portion of the opening, the top end of the connection member is made to be lower than the surface of the interlayer insulating film. Thus, oxidation of the connection member can be prevented when the capacitor dielectric film is formed.
The method of manufacturing the semiconductor device according to the ninth aspect of the present invention is different from the conventional manufacturing method in that the lower electrode of the capacitor is the metal electrode, the major component element of which is ruthenium or iridium, the silicide layer is formed between the metal electrode and the connection member, and the capacitor dielectric film, made of the material having a large dielectric constant, and the upper electrode of the capacitor are formed on the metal electrode in such a manner that no oxide layer of the materials of the metal electrode is formed on the surface of the metal electrode. Therefore, the semiconductor device having the variety of advantages can easily be manufactured. Since the connection member containing silicon as the major component is buried in only a portion of the opening, the top end of the connection member is made to be lower than the surface of the interlayer insulating film. Thus, oxidation of the connection member can be prevented when the capacitor dielectric film is formed.
The method of manufacturing the semiconductor device according to the tenth aspect of the present invention enables the advantages similar to those obtainable from the method of manufacturing the semiconductor device according to any one of the sixth to ninth aspects of the present invention to be realized. Since the surface of the lower electrode of the capacitor can be flattened by the chemical and mechanical grinding method after the lower electrode of the capacitor has been formed, enlargement of the leakage current can be prevented.
The method of manufacturing the semiconductor device according to the eleventh aspect of the present invention enables advantages similar to those obtainable from the method of manufacturing the semiconductor device according to any of the sixth to tenth aspects of the present invention to be realized. Since the adhesion layer is formed between the interlayer insulating film and the lower electrode of the capacitor, the adherence between the interlayer insulating film and the lower electrode of the capacitor can be improved.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.